There is a continued and increasing interest of delivery of Over-the-top (OTT) services in cellular networks. Such OTT services may e.g. be video, television or other services provided over the Internet. Today these services are delivered as normal best effort (BE) traffic. However, in some cases the OTT applications would require specific treatment in order to get a satisfactory experience at the receiver side, often referred to as quality of experience (QoE). This is the case e.g., for Internet video traffic, which is getting more and more prevalent in mobile broadband traffic.
Video applications are sometimes controlled either from client or server side in order to cope with the fluctuating bandwidth of the Internet. Based on experienced throughput, the video quality, and consequently the required bandwidth, is changed. In this way a seamless play-out may be guaranteed as long as there is content in a play-out buffer of a video player to serve. In case of buffer underrun, i.e. the play-out buffer runs empty, the picture freezes and the play-out waits until the size of the buffered video data in the play-out buffer again reaches a pre-configured threshold for continued play-out. A rotating symbol on the screen may show the end-user that the video player is waiting for new data.
New deployments of chunk-based streaming video applications may infer a large problem when resources for application data delivery are not sufficient. When a chunk of application data has been downloaded the video may start to play but it may stop before the next chunk has arrived in the play-out buffer. This means that the play-out may experience frequent and repetitive frozen image events during a session, which can lead to a very low quality of experience as perceived by the end-user.
The term “quality of experience” (QoE) will be used herein to refer to quality of an application session which may be perceived by an end-user and influences a user's experience of the application session. In case of a video application session, a measure of the QoE may include such parameters as number of frozen image events during a session, duration of frozen image events and latency, i.e. time from initiation of the video application service until the play-out of the video starts. The QoE is related to but differs from the quality of service (QoS). As used herein the term “quality of service” relates to the quality of a bearer set-up in a communication network. Again using the example of the video application session, the end-user may not notice any difference in the play-out of the video if the QoS changes as long as the QoS is sufficient to keep the play-out buffer from underrun. However, poor QoS may lead to events of play-out buffer underrun which impacts the QoE. Hence QoE relates to quality on an application level, while QoS relates to quality on a bearer level.
Delivery of content related to e.g. OTT services is qualitatively different in case of a mobile access compared to cases with fixed access. In case of e.g. Internet video streaming a larger number of video freeze/rebuffering events can be expected with mobile access than with fixed access, especially if the content is served in interactive radio bearers, together with other BE traffic. The reason is that there is a bottleneck on the ‘first mile’, namely in the form of limited bandwidth resources over the radio interface. This means that the statistical traffic fluctuations on the bottleneck link, i.e. over the radio interface, are large. In addition, the available capacity per mobile terminal also depends on the channel quality experienced. Thus the capacity that is available for a subscriber is rather unpredictable and depends on the subscriber's position, velocity and other subscribers' position and activity as well.
One straightforward solution for controlling delivery of application data to or from a mobile terminal would be to apply a standard QoS architecture in line with the 3rd Generation Partnership Program (3GPP) standard to guarantee a required long-term throughput for all packet data applications by setting up guaranteed bit-rate (GBR) bearers towards the mobile terminal. A description of such a solution can be found in the standard document 3GPP TS 23.401 V9.1.0 (2009-06), General Packet Radio Service enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access (Release 9). It can be understood that there are potential scalability problems of bearer setup signaling with this solution. Furthermore, it is obvious that this solution would result in a relatively low number of serviced OTT requests due to the limited number of high-priority, e.g., GBR bearers that may be allowed in the system. Accordingly there is a problem of radio spectrum efficiency associated with this solution.
Another method for controlling delivery of application data in case of a mobile access has been proposed in the international patent application with publication No. WO 2010/088490 A1 and is based on traffic throttling. According to this method, media content is segmented into smaller parts (e.g., corresponding to a 2-minute presentation in case of a video service) and each segment is scheduled based on the estimated presentation time, i.e., the time when the given part is needed in the application session. The goal is that the delivery time for the segment should be less, but not much less, than the presentation time. By delaying some of the segments of a bearer with good radio conditions the content from the other bearers get higher chance to be delivered in time. However, throttling of traffic is generally not spectrum-efficient since it may leave some radio capacity unused even if there would be traffic to send. In the case of packet data applications, for example, such periods could be used to pre-fill play-out buffers that could pay off at a later time of potential congestion.